This invention concerns improvements in and relating to stranding machines such as are utilised for the production of wire ropes, electrical cables, or the like. More particularly, the invention relates to an improved mechanism for use in loading and unloading the wire supply bobbins to be installed in a wire stranding machine.
In the operation of a wire stranding machine, the productivity that may be obtained from the machine is determined not only by the speed at which the machine itself can be run, but by the time required for loading and unloading the wire supply bobbins to be installed in the machine, during which time the machine is at a standstill. In machines incorporating a large number of relatively heavy wire supply bobbins, the time required for changing bobbins to reload the machine has occupied a relatively large proportion of the operating cycle of the machine, and thus a variety of attempts have been made to reduce the loading time in these machines.
The requirement for easy access to the stranding machine to facilitate loading has led to the development of the so-called fork type stranding machine, wherein bobbins disposed in groups spaced along the rotary axis of the machine are mounted in a manner such that the bobbins of each group are held in fork-shaped trunnions extending radially from the rotary axis of the machine. This enables the simultaneous replacement of a plurality of bobbins utilising a cradle arranged to receive a row of bobbins extending axially of the machine. By indexing the machine into a predetermined angular position wherein one bobbin of each of the relatively axially spaced groups within the machine is located in a predetermined, common radial position with respect to the rotary axis of the machine, simultaneous replacement of the bobbins can be effected by moving a corresponding cradle radially towards and away from the rotary axis of the machine to engage, remove and replace the bobbins.
The annular position from which the bobbins are removed and replaced is determined by the selected method of handling the cradles containing bobbins. In one previously proposed arrangement, bobbins are inserted and removed from a point vertically above the axis of the machine, utilising an appropriate mechanical crane. In another arrangement, bobbins are inserted and replaced along a horizontal axis utilising a fork lift truck. In yet another proposed arrangement bobbins may be inserted and removed from vertically below the rotary axis of the machine, utilising an elevating platform installed directly below the machine.
All of the above proposed arrangements have significant drawbacks. When using a crane or fork lift truck to handle bobbins or bobbin cradles, the precision with which the bobbins can be located relatively to the machine during installation is a function of human judgement, and thus time is consumed in appropriately indexing the rotary machine and adjusting the positions of the bobbins until they register with the trunnions of the machine. In the case where bobbins are elevated from vertically below the axis of the machine, the procedure is complicated by restricted access to the machine and the difficulty in readily inspecting the installed bobbins at such a position in the machine.
Accordingly, there is a requirement for a more convenient and more rapid arrangement for installing supply bobbins in rotary stranding machines.